New preparation process of a catalyst for converting aromatic hydrocarbons

ABSTRACT

Process for manufacturing a catalyst for hydrocarbon conversion consisting of a mordenite containing less than 0.5% by weight ofsodium, having a molar ratio SiO 2  /Al 2  O 3  from 10 to 100 and further containing at least one metal selected from cobalt, nickel, silver and palladium, wherein said metal in incorporated to a mordenite of the sodic form having a molar ratio SiO 2  /Al 2  O 3  close to 10, the major portion of the sodium is eliminated, the resulting catalyst mass is dried from about 50° to 150° C. and then subjected to a first so-called dry calcination between 300° and 700° C., in the presence of a dry, inert or oxidizing gas containing less than 1% by volume of steam, and to a second so-called wet calcination between 250° and 700° C., in the presence of either steam or an inert or oxidizing gas containing at least 3% of steam.

This is a division of application Ser. No. 842,132, filed Oct. 14, 1977.

This invention relates to the catalytic conversion of aromatichydrocarbons. More precisely, it is concerned with the dismutation ofalkyl aromatic hydrocarbons such as toluene, so as to produce benzeneand xylenes, or the transalkylation of alkylaromatic hydrocarbons, suchas toluene and trimethylbenzenes, to produce xylenes.

It is an object of this invention to provide a new process for preparinga catalyst for toluene dismutation and/or toluene and C₉ ⁺ aromatichydrocarbons transalkylation, of high activity and selectivity andhaving an improved stability as compared to the catalyst of the priorart. This catalyst for converting hydrocarbons consists of a mordenitecalcined in the presence of steam, in which the molar ratio SiO₂ /Al₂ O₃is from about 10 to 100, preferably from 10 to 50, and having a contentof less than 0.5% by weight of sodium ions and preferably less than 0.3%by weight of sodium ions.

The catalyst used according to this invention is a mordenite containingions of one or more metals selected from cobalt, nickel, silver andpalladium. When the selected metal is nickel, the mordenite may alsoadvantageously contain copper.

Many dismutation and transalkylation catalysts have already beendescribed in the prior art. The most efficient contain zeolites as thebase, and more particularly, the so-called "wide pore" mordenite in itshydrogen form, as described in U.S. Pat. No. 3,506,731. In the U.S. Pat.Nos. 3,281,483 mentions mordenites essentially exchanged with nickel orsilver ions, 3,780,121 includes a statement relating to a mordeniteexchanged with ions of group 1B metals and characterized by a molarratio SiO₂ /Al₂ O₃ in the range from 12 to 80, 3,629,351 also concerns amordenite containing ions of metals from groups 1B, VA, VIA, VIIA andVIII, and 3,476,821 claims the use of a mordenite containing asulfurized metal from group VIII and having preferably a molar ratioSiO₂ /Al₂ O₃ higher than 20. However none of these patents mentions oreven suggests the particular technique of calcination under wetatmosphere according to the present invention, said technique beingstrictly necessary during the preparation of the catalyst, in order toobtain a catalyst having the simultaneous properties of being active,stable during time and, overall, very selective in the aromatichydrocarbon dismutation or transalkylation reactions. Whereas a wetcalcination technique is described in U.S. Pat. No. 3,720,726 for amordenite used in sodium form or hydrogen form, this technique differsfrom the present technique and is clearly less efficient for mordenitescontaining cobalt, nickel, silver and/or palladium.

The preparation of the catalyst and particularly the calcination step inthe presence of steam according to the methods of the present invention,leads to catalyst formulas resulting in substantially improvedperformances, particularly as concerns activity, selectivity andstability during time, as compared with the catalysts prepared accordingto the methods of the prior art as examplified in the above-mentionedpatents.

The zeolite used as the base for the preparation of the catalyst of theinvention, is the so-called "wide pore" mordenite of sodium form as, forexample, that available in the trade under the name of Zeolon Na,manufactured by NORTON Society. This mordenite has a molar ratio SiO₂/Al₂ O₃ substantially equal to 10. This mordenite, which will bereferred to hereinafter as Na-M, has pore openings of about from 7 to 8Angstroms, which makes it possible for aromatic molecules such aspolymethylbenzene hydrocarbons having up to 12 carbon atoms permolecule, for example, to fit in the pores.

For the manufacture of the catalyst of the invention, it is firstnecessary to extract, as above-mentioned, the major part of the sodiumions of the "wide pore" mordenite Na-M and to replace these ions withone or more of the following ions: Co⁺⁺, Ni⁺⁺, Ag⁺ and Pd⁺⁺.

It is known that the most common method for obtaining the protonic form(as "hydrogen" form) which will be referred to as HM, consists oftreating the zeolite of sodic form Na-M in an aqueous solution of aninorganic acid. It is also known that, in order to have the mordeniteexchanged with ammonium ions, which will be referred to as NH₄ -M, thesolid is generally allowed to remain in an aqueous solution of ammoniumsalt.

In order to obtain the mordenite exchange with at least one of themetals selected from Co, Ni, Ag and/or Pd, it is possible directlyexchange the sodium ions of the mordenite Na-M with the metal ionsselected from cobalt, nickel, silver and palladium, which are to beintroduced. It is also possible to exchange the sodium ions first withH⁺ ions or with NH₄ ⁺ ions and, subsequently, to introduce the desiredmetals either by ionic exchange or by the so-called dry impregnation(without excess of solution) or by impregnation with an excess ofsolution. When the desired catalyst must contain several of these metals(Co, Ni, Ag, Pd), the latter may be introduced either each in the samemanner or each according to a different method. In the case where theoperation is conducted by ion exchange, the various metal cations may beintroduced either simultaneously in a single or several operations ofcation exchange, by means of solutions containing in admixture severalor the all the cations, or successively, by a series of exchanges, eachinvolving a single type of cation. When the metal which is destined toreplace the sodium is expensive, this being for example the case ofsilver, it will be preferable, in order to reduce the cost, topreliminarily exchange the sodium with ammonium ions.

The above mentioned treatment for the preparation of HM mordenite inacid solution has in fact, two separate effects: on the one hand, anattack of the aluminosilicate lattice occurs which results in anextraction of the aluminum atoms and, consequently, in an increase ofthe ratio Si/Al of the frame; on the other hand, cations of the zeoliteare replaced by protons.

This attack of the lattice increases in importance as the treatment islengthened, and as acid concentration and the temperature of thesolution is increased. By such a treatment, it is possible to preparemordenites of reduced aluminum content having a molar ratio SiO₂ /Al₂ O₃higher than 10 or even higher than 1,000. It is known that suchmordenites of low aluminum content have acid properties different fromthose of the normal mordenite HM; a maximum acidicity is generallyobtained for values of the molar ratio SiO₂ /Al₂ O₃ in the range from 10to 100. It is possible to introduce in the structure of such mordenitesof low aluminum content, cations of the selected metals (Co, Ni, Ag, Pd)according to techniques similar to those described above.

The total ion contents of the desired metals in the mordenite may befrom 0.01 to 25% by weight, but the preferred contents are from 0.1 to8% by weight for cobalt and nickel, from 0.2 to 18% by weight for silverand from 0.01 to 5% by weight for palladium.

When the metal is nickel (clearly more hydrogenolyzing than silver,cobalt and palladium), it is possible to add from 0.001 to 1% by weightof copper to the mordenite; as a matter of fact, it has been observedthat copper, combined with nickel, contributes to the disappearance ofthe hydrogenolyzing properties (which result, for example, in methaneformation) which may be caused by nickel after calcination under wetatmosphere.

The highest values correspond to contents which cannot always beobtained by ion exchange. Thus the maximum cation exchange rate of 100%corresponds, with nickel, to 7.5% by weight of metal and, with silver,to about 23% by weight. Moreover, the exchange rate of 100% is notalways achievable in practice: with nickel, for example, it is notpossible to introduce more than about 3% by weight of metal. Valueshigher than these maximum contents could not therefore be obtainedexcept by impregnation.

Whatever may be the method used, either by ion exchange or impregnation,a relatively substantial amount of the metal ions present in the solidis not fixed to the latter but remains in the form of cations in thesolution filling the pores. During the drying or the calcination, thecations tend to be collected and result in the formation of more or lesslarge crystallites of metal oxides or hydroxides which will be locatedin the macroporosity. These oxides may then be reduced to the metalstate in the presence of hydrogen at high temperature. It can beobserved, for example, that crystallites of nickel having a size ofabout 200-300 Angstroms are present in the reduced Ni Mordenite. Thesemetal crystallites are responsible for the occurrence of reactions whichare highly undesirable for the dismutation, such as:

hydrogenation of aromatics to naphthenes,

hydrogenolyzis with formation of methane and ethane,

coke formation.

The parasitic hydrogenation of aromatics is a very troublesome reactionsince it results in the occurrence, in the benzene cut, of substantialamounts of saturated products which may require the performance of anextractive distillation in addition to the conventional distillation, inorder to obtain a very pure benzene, in particular free of cyclohexane.The parasitic hydrogenolysis is responsible for a loss of aromatic ringsand accordingly for a decrease of the yield in aromatics of theoperation. Finally, the parasitic formation of coke may result in aclogging of the micropores of the zeolite and therefore in a very rapiddrop of activity of the latter.

On the contrary, these undesirable reactions do not occur at all, or atleast are reduced to an acceptable level, when the metal or metalsproduced in the solid, are dispersed to an almost atomic state in thezeolite structure. In order to avoid, or at least to reduce, thecollection of the metals in the form of oxides crystallites which, afterreduction, become metal crystallites, it has been suggested, in variouspatents, to proceed with particular care during certain steps of themordenite preparation. It has thus been proposed to control the pH ofthe exchange solutions in order to avoid the formation of hydroxidemicroprecipitate at the surface of the zeolite, NH₄ form for example,whose reaction in solution is very slightly basic (pH of about 7 to8.5). It has also been proposed to conduct that exchange at temperaturefrom 80° to 150° C., so as to introduce a larger amount of cations inthe structure, and to proceed to a very careful washing of the solidafter the ion exchange, so as to progressively remove all the cationsremaining in solution (see French Pat. No. 2 033 853).

These various precautionary measures actually result in a significantimprovement of the catalyst performances but, however, do not result insuch a conclusive improvement as that obtained according to theinvention. As a matter of fact, even a very severe control of the pHdoes not always permit an avoidance of the collection of polyatomicspecies at the surface of the solid. Thus, in the case, for example, ofnickel, the slope of the curves of neutralization, by ammonia, of nickelnitrate solutions, seems to indicate a condensation of the cations insolution resulting in the formation of a polycationic species which,when neutralizing a negative site of the solid, already constitutes thestarting of a collection. Moreover, a careful washing of the solidcannot be performed on a mordenite ipregnated either with an excess ofsolution or not, without the liability of losing all of the advantage ofthis operation, (this advantage being of making possible theintroduction of a metal amount greater than that possible by simpleionic exchange). The impregnation method thus results unavoidably in theformation of large crystallites of metal oxide or of metal within themacroporosity and, consequently, in the production of catalysts of lowselectivity and low stability. Moreover, a washing, even very careful,of the exchanged zeolites does not completely avoid the formation ofthese large crystallites. These metal crystallites may constitutecrystallization nucleii on which still dispersed metal atoms are liableto become agglomerated and which migrate in the structure during thereaction under the effect of the temperature. This latter phenomenon mayalso be responsible for the deactivation of the catalyst.

In view of all these problems, each step of the preparation of thezeolite catalyst is important and must be carried out with care.However, all these steps have not the same importance and only a fewnumber thereof are really key points in the preparation since they are,for the most part, responsible for the obtainment of the optimalproperties of the catalyst; even in some cases, they can compensate forcertain imperfections obtained in the course of the preceding steps.

It has thus been discovered, according to the present invention, thatthe calcination of the catalyst is a fundamental step of the preparationand that it permits, when properly carried out, the production ofcatalysts which are simultaneously active, selective and stable duringtime, from mordenites exchanged and roughly washed or impregnated with asolution of a metal salt. As a matter of fact, it has been made apparentthat, when the calcination is carried out according to a form ofprocedure which will be defined below, in neutral or oxidizingatmosphere and in the presence of steam at temperatures not in excess of700° C., the resulting catalysts do not suffer from the above-mentioneddrawbacks relating to stability and selectivity, while retaining theadvantage of an excellent activity.

Precautionary measures must be taken during the calcination in thepresence of steam. Thus, it has been observed that for mordenites,containing cobalt, nickel, silver or palladium, it is not proper (aftera preliminary drying of the catalyst at 50° to 150° C.), to proceeddirectly to a calcination in wet atmosphere. As a matter of fact, it hasbeen observed for example, that after a preliminary drying between 50°an 150° C., a direct treatment of a Ni-M or Co-M or Ag-M of Pd-M zeolitewith steam or with a gas containing the same, produces a grey-blackcoloured solid which, after conventional reduction with hydrogen at 450°C., has a very poor selectivity in the dismutation process: a verysubstantial degradation of the toluene, of the order of from 30 to 70%,by hydrogenation or hydrogenalysis is observed under the usualconditions of the test (420° C.--30 bars--H₂ /HC=5-VVH=4).

It has also been observed that for mordenites containing nickel, cobalt,silver and/or palladium, it is not proper to proceed as described inU.S. Pat. No. 3,720,726, i.e. to dry the catalyst and then to completethe manufacturing process first by a calcination in wet atmosphere andthen by calcination in dry atmosphere. This method is only suitable forthe form Na-M.

On the contrary, it is more convenient to subject the zeolites Ni-M,Co-M, Ag-M or Pd-M to the following steps in successive order:

(a) a drying of a few hours (from 2 to 15 hours for example) at atemperature about from 50° to 150° C., generally under atmosphericpressure;

(b) a so-called "dry" calcination, between 300° and 700° C., in thepresence of a dry gas, either inert (nitrogen) or oxidizing (preferablyair) containing less than 1% by volume of steam (dew point lower than 7°C. in the case of air) and preferably less than 0.25% by volume of steam(dew point lower than 10° C. in the case of air) and, then

(c) a so-called "wet" calcination.

The solid obtained as final product has a pale beige color and exhibitscatalytic properties (activity, selectivity, stability) which areimproved as compared to those of Ni-M, Co-M, Ag-M, Pd-M mordenites,obtained according to other methods.

The so-called "wet" calcination of the present invention, is performedby treatment with an atmosphere containing steam and optionally at leastone other gas, either oxidizing or inert. More precisely, the atmosphereused for the so-called "wet" treatment, consists of:

either pure steam

or a mixture of steam with an inert gas, such as argon, nitrogen, etc.,this mixture containing less than 100% and at least 3% of steam byvolume, and preferably, at least 10% of steam by volume;

or a mixture of steam with an oxidizing gas (oxygen, air, gas containingmolecular oxygen), this mixture containing at least 3% by volume ofsteam (and preferably at least 10% by volume) and less than 100% ofsteam;

or a mixture

(a) of steam and

(b) of a mixture of an inert gas with an oxidizing gas, the totalmixture containing less than 100% and at least 3% by volume of steam,and preferably at least 10% by volume of steam.

It will be observed that the value of 3% by volume is higher than thatcorresponding to air saturated with steam at 20° C. (dew point=20° C.,steam pressure=17.5 mm of mercury, percent water in air by volume=2.3%).This treatment with steam or with a gas containing the same, isperformed between 250° and 700° C., preferably between 300° and 650° C.or, still preferably, between 350° and 600° C., under a pressure from0.1 to 50 bars, preferably from 0.5 to 10 bars, during periods from 1minute to 10 days, according to the temperature, the pressure and theatmosphere selected for the treatment.

It will be observed that the wet treatment may directly follow thecalcination under dry atmosphere (i.e., without intermediary cooling) ormay be separated from said dry calcination by a cooling step, eitherslowly (under scavenging with a neutral or oxidizing gas), or suddenly(by means of a cooled gas or by contact of the hot solid with cold waterfor example). The catalyst may thus be cooled down to any temperature,for example around ambient temperature.

The catalyst which, on the one hand, has been subjected to a wettreatment according to the method of the present invention and, on theother hand, has been subjected to a conventional reduction withhydrogen, for example between 300° and 500° C., under 1 to 10 bars, for1 to 10 hours, may be used in the dismutation reactions of toluene tobenzene and xylenes and transalkylation reactions of toluene andtrimethylbenzenes to xylenes under the following conditions: temperaturefrom 350° to 550° C., preferably from 400° to 500° C., pressure from 10to 50 bars, preferably from 20 to 40 bars; feed space velocity,expressed in grams of feed charge per gram of catalyst and per hour,from 0.1 to 10 and, preferably, from 0.5 to 4; molar ratiohydrogen/hydrocarbon in the range from 3 to 20 and preferably from 5 to14.

The following non limitative examples illustrate the invention.

EXAMPLE 1

The object of this experiment is to prepare mordenites exchanged withNH₄ ⁺ or H⁺ ions. The two mordenites M₁ (NH₄ -M) and M₂ (H-M) areprepared as follows:

M₁ (NH₄ -M): 700 g of sodic mordenite Na-M of the zeolon Na type, asextrudates of 1/16th of inch, are subjected to four successive exchangesin 3.5 liters of a molar solution in ammonium nitrate, adjusted to a pH7 by addition of ammonia, at room temperature for 6 hours understirring. The solid is filtered, washed and dried at 85° C. for 6 hours.Example 3 indicates how calcination of M₁ is performed.

M₂ (H-M): 200 g of sodium mordenite Na-M, (the same as that used for thepreparation of M₁) are subjected to two successive exchanges in oneliter of a molar solution of ammonium nitrate and then immersed in 2liters of a 4N solution of hydrochloric acid at 80° C. for 30 hours. Thesolid is filtered, washed, and dried at 85° C. for 6 hours. Example 3indicates how M₂ is calcined.

EXAMPLE 2

The purpose of the experiment is to prepare mordenites exchanged withcobalt, nickel or silver M₃, M₄, M₅, M₆ and M₇. The clacination methodsare indicated hereinafter in example 3.

M₃ (Co-M): 100 g of uncalcined solid M₁ are immersed in 1 liter of amolar solution of cobalt nitrate adjusted to a pH 7 by ammonia addition.The solution is stirred at room temperature for 6 hours.

M₄ (Ni-M): 100 g of uncalcined solid M₁ are immersed in 1 liter of amolar solution of nickel nitrate, adjusted to a pH 7 by ammoniaaddition. The solution is stirred at room temperature for 6 hours.

M₅ (Ag-M): 100 g of uncalcined solid M₁ are immersed in 1 liter of amolar solution of silver nitrate diamine NO₃ Ag(NH₃)₂ of about pH 9. Thesolution is stirred at room temperature for 6 hours.

M₆ (Ni-M): 50 g of uncalcined solid M₂ are exchanged with a solution ofnickel nitrate according to a technique identical to that of solid M₄.

M₇ (Ag-M): 50 g of uncalcined solid M₂ are exchanged with a solution ofsilver nitrate diamine according to a technique identical to that ofsolid M₅.

These samples M₃ to M₇ are all subjected to a drying step at 85° C., for6 hours, in an air-drying oven.

EXAMPLE 3

Calcination of various samples.

4 types of calcination have been performed on various samples,preliminary dried at 85° C., for 6 hours, in an air drying oven:

(1) calcination at 500° C., for 3 hours, under atmospheric pressure,with a very dry air stream (100 l/h), predried over silica-gel and thendried over a molecular sieve 13X;

(2) direct calcination of the solid under wet air (50% of steam ingaseous volume) with a flow rate of the total gaseous stream of 100 l/hat 500° C. for 3 hours under atmospheric pressure;

(3) calcination under very dry air (H₂ O<0.1% by volume) at 500° C. for2 hours under atmospheric pressure (100 l/h), followed with the contentof the solid, at this temperature and under atmospheric pressure, withan atmosphere consisting of 95% of steam and 5% of air, for 2 hours (100l/h). No cooling is performed between these two calcination steps;

(4) calcination with wet air (50% of steam in gaseous volume) at a totalflow rate of the gaseous stream of 100 l/h, at 500° C. for 3 hours underatmospheric pressure, followed with the contact of the solid at 500° C.,under atmospheric pressure, with a very dry air stream (500 l/h) (H₂O<0.1% by volume), for 2 hours.

The analyzis of the samples M₁ to M₇ are reported in table I below. Forany given sample, the results of the analysis are the same, irrespectiveof the method selected for the calcination.

                  TABLE 1                                                         ______________________________________                                                                     %                                                                   SiO.sub.2 /Al.sub.2 O.sub.3                                                             by weight                                                                             % metal                                  CATALYST CATION    Molar     Na      by weight                                ______________________________________                                        M.sub.1  NH.sub.4  10.9      0.30                                             M.sub.2  H         25.1      0.12                                             M.sub.3  Co        10.9      <0.30   1.9                                      M.sub.4  Ni        10.9      <0.30   1.5                                      M.sub.5  Ag        10.9      <0.30   16.7                                     M.sub.6  Ni        25.1      <0.12   0.8                                      M.sub.7  Ag        25.1      <0.12   13.8                                     ______________________________________                                    

The various samples M₁ to M₇ are referred to hereinafter, according totheir type of calcination and by the following code: (the letter "d" isused for indicating "dry," the letter "w" for indicating "wet").

M^(d) for the first type of calcination (dry air), does not conform tothe invention.

M^(w) for the second type (wet air), does not conform to the invention.

M^(dw) for the third type (dry air followed with wet air), conforms tothe invention.

M^(wd) for the fourth type (wet air followed with dry air), does notconform to the invention.

The following samples have been prepared:

M₁ ^(d), M₂ ^(d), M₃ ^(d), M₄ ^(d), M₅ ^(d), M₆ ^(d), M₇ ^(d)

M₁ ^(w), M₂ ^(w), M₃ ^(w), M₄ ^(w), M₅ ^(w)

M₁ ^(dw), M₂ ^(dw), M₃ ^(dw), M₄ ^(dw), M₅ ^(dw), M₆ ^(dw), M₇ ^(dw)

M₁ ^(wd), M₂ ^(wd), M₃ ^(wd), M₄ ^(wd), M₅ ^(wd)

The so-prepared catalysts, before being used, are subjected to areduction with hydrogen at 450° C., for 2 hours and under 1 bar.

All the catalysts are then subjected to a test of toluene dismutationunder the following conditions:

T°C.=420

P bars=30

feed space velocity=5 g of toluene/hour and g of catalyst

molar ratio H₂ /HC=5

The results of the catalytic tests are reported in the following sets oftables 2 to 8. These various tables show the evolution, during time, ofthe total conversion by weight of toluene, of the loss, in percent byweight, of aromatics, of the content, in percent by weight, respectivelyof benzene and of C₈ aromatics in the total of aromatics and of thecontent, in percent by weight, of ethylbenzene in C₈ aromatics. Theactivity is shown by the conversion rate, the selectivity by the loss inaromatics and also by the amount of benzene and C₈ aromatics in thearomatic fraction.

EXAMPLE 4

Results of tests with catalysts M₁ ^(d) to M₇ ^(d), calcinated undervery dry air atmosphere.

These results are reported in tables 2, 3 and 4 below.

                                      TABLE 2                                     __________________________________________________________________________                               Ethylbenzene                                          Conversion                                                                          Loss of     C.sub.8                                                                             in C.sub.8                                         Time                                                                             rate  aromatics                                                                           Benzene                                                                             Aromatics                                                                           aromatics                                          (h)                                                                              M.sub.1.sup.d                                                                    M.sub.2.sup.d                                                                    M.sub.1.sup.d                                                                    M.sub.2.sup.d                                                                    M.sub.1.sup.d                                                                    M.sub.2.sup.d                                                                    M.sub.1.sup.d                                                                    M.sub.2.sup.d                                                                    M.sub.1.sup.d                                                                     M.sub.2.sup.d                                  __________________________________________________________________________     1 22.1                                                                             25.2                                                                             5.1                                                                              7.9                                                                              7.2                                                                              7.4                                                                              8.3                                                                              8.4                                                                              2.7 3.5                                             3 19.0                                                                             20.1                                                                             3.7                                                                              5.1                                                                              6.5                                                                              6.0                                                                              7.4                                                                              6.9                                                                              2.1 3.1                                            10 15.5                                                                             11.3                                                                             2.9                                                                              4.3                                                                              5.3                                                                              2.9                                                                              6.1                                                                              3.4                                                                              1.9 3.1                                            30 10.1                                                                              4.8                                                                             2.9                                                                              2.2                                                                              3.0                                                                              0.7                                                                              3.4                                                                              0.8                                                                              1.7 2.8                                            __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________                                            Ethylbenzene                              Conversion                                                                             Loss of           C.sub.8  in C.sub.8                            TIME                                                                              rate     Aromatics                                                                              Benzene  aromatics                                                                              aromatics                             (h) M.sub.3.sup.d                                                                    M.sub.4.sup.d                                                                    M.sub.5.sup.d                                                                    M.sub.3.sup.d                                                                    M.sub.4.sup.d                                                                    M.sub.5.sup.d                                                                    M.sub.3.sup.d                                                                    M.sub.4.sup.d                                                                    M.sub.5.sup.d                                                                    M.sub.3.sup.d                                                                    M.sub.4.sup.d                                                                    M.sub.5.sup.d                                                                    M.sub.3.sup.d                                                                    M.sub.4.sup.d                                                                    M.sub.5.sup.d                   __________________________________________________________________________     1  20.1                                                                             26.2                                                                             25.9                                                                             9.7                                                                              10.4                                                                             7.2                                                                              4.4                                                                              6.7                                                                              8.0                                                                              5.0                                                                              7.7                                                                              9.1                                                                              3.4                                                                              3.6                                                                              2.9                              3  20.1                                                                             22.8                                                                             23.1                                                                             8.4                                                                              8.6                                                                              6.6                                                                              4.9                                                                              6.0                                                                              7.0                                                                              5.7                                                                              6.9                                                                              8.0                                                                              2.8                                                                              3.3                                                                              2.5                             10  17.2                                                                             19.1                                                                             20.5                                                                             6.8                                                                              6.5                                                                              5.1                                                                              4.4                                                                              5.3                                                                              6.5                                                                              5.1                                                                              6.1                                                                              7.5                                                                              2.8                                                                              3.1                                                                              2.2                             30  12.8                                                                             13.2                                                                             15.5                                                                             4.3                                                                              5.5                                                                              4.3                                                                              3.6                                                                              3.2                                                                              4.7                                                                              4.1                                                                              3.7                                                                              5.4                                                                              2.1                                                                              2.7                                                                              1.9                             __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________                                Ethylbenzene                                          Conversion                                                                          Loss of     C.sub.8                                                                             in C.sub.8                                        TIME                                                                              rate  Aromatics                                                                           Benzene                                                                             Aromatics                                                                           aromatics                                         (h) M.sub.6.sup.d                                                                    M.sub.7.sup.d                                                                    M.sub.6.sup.d                                                                    M.sub.7.sup.d                                                                    M.sub.6.sup.d                                                                    M.sub.7.sup.d                                                                    M.sub.6.sup.d                                                                    M.sub.7.sup.d                                                                    M.sub.6.sup.d                                                                     M.sub.7.sup.d                                 __________________________________________________________________________     1  31.7                                                                             29.4                                                                             10.7                                                                             9.2                                                                              9.0                                                                              8.6                                                                              10.2                                                                             9.8                                                                              3.5 3,8                                            3  24.7                                                                             22.8                                                                             7.1                                                                              8.1                                                                              7.5                                                                              6.2                                                                              8.6                                                                              7.1                                                                              3.1 3.6                                           10  15.5                                                                             16.1                                                                             4.8                                                                              6.0                                                                              4.5                                                                              4.3                                                                              5.2                                                                              4.9                                                                              2.7 3.2                                           30  5.5                                                                              6.4                                                                              3.1                                                                              4.2                                                                              1.0                                                                              0.9                                                                              1.1                                                                              1.1                                                                              2.5 2.9                                           __________________________________________________________________________

It is observed particularly that mordenites M₂, M₆ and M₇ which havebeen subjected to an acid treatment, either exchanged or not withtransition ions, have a higher initial activity but lose their activitymore rapidly during time than the corresponding zeolites which have notbeen subjected to an acid treatment.

EXAMPLE 5

Results of the tests with catalysts M₁ ^(w), M₂ ^(w), M₃ ^(w), M₄ ^(w)and M₅ ^(w), directly calcinated under wet air atmosphere.

The results are reported in the following tables 5 and 6:

                                      TABLE 5                                     __________________________________________________________________________                                Ethylbenzene                                          Conversion                                                                          Loss of     C.sub.8                                                                             in C.sub.8                                        TIME                                                                              rate  Aromatics                                                                           Benzene                                                                             Aromatics                                                                           Aromatics                                         (h) M.sub.1.sup.w                                                                    M.sub.4.sup.w                                                                    M.sub.1.sup.w                                                                    M.sub.4.sup.w                                                                    M.sub.1.sup.w                                                                    M.sub.4.sup.w                                                                    M.sub.1.sup.w                                                                    M.sub.4.sup.w                                                                    M.sub.1.sup.w                                                                     M.sub.4.sup.w                                 __________________________________________________________________________     1  31.5                                                                             80.8                                                                             1.8                                                                              55 12.7                                                                             10.9                                                                             14.5                                                                             12.6                                                                             1.4 1.3                                            3  29.2                                                                             81.3                                                                             1.4                                                                              56 11.9                                                                             10.7                                                                             13.6                                                                             12.3                                                                             1.3 1.1                                           10  25.1                                                                             79.7                                                                             0.9                                                                              55 10.3                                                                             10.6                                                                             11.8                                                                             12.1                                                                             1.1 1.0                                           30  17.3                                                                             72.6                                                                             0.5                                                                              54 7.1                                                                              7.9                                                                              8.2                                                                              9.0                                                                              1.0 0.9                                           __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________                                            Ethylbenzene                              convenrsion                                                                            Loss of           C.sub.8  in C.sub.8                            TIME                                                                              rate     Aromatics                                                        __________________________________________________________________________     Benzene                       Aromatics                                                                              Aromatics                             (h) M.sub.2.sup.w                                                                    M.sub.3.sup.2                                                                    M.sub.5.sup.2                                                                    M.sub.2.sup.2                                                                    M.sub.3.sup.2                                                                    M.sub.5.sup.2                                                                    M.sub.2.sup.2                                                                    M.sub.3.sup.2                                                                    M.sub.5.sup.2                                                                    M.sub.2.sup.2                                                                    M.sub.3.sup.2                                                                    M.sub.5.sup.2                                                                    M.sub.2.sup.2                                                                    M.sub.3.sup.2                                                                    M.sub.5.sup.2                   __________________________________________________________________________     1  25.2                                                                             31.3                                                                             40.6                                                                             7.9                                                                              15.1                                                                             8.2                                                                              7.4                                                                              6.8                                                                              14.2                                                                             2.4                                                                              7.9                                                                              16.4                                                                             3.5                                                                              2.5                                                                              1.8                              3  20.1                                                                             28.7                                                                             40.2                                                                             5.1                                                                              14.3                                                                             8.0                                                                              6.1                                                                              6.0                                                                              14.1                                                                             16.9                                                                             7.0                                                                              16.3                                                                             3.1                                                                              2.3                                                                              1.6                             10  11.4                                                                             26.7                                                                             38.1                                                                             4.3                                                                              13.8                                                                             6.5                                                                              3.0                                                                              5.3                                                                              13.9                                                                             3.6                                                                              6.2                                                                              16.0                                                                             3.2                                                                              2.3                                                                              1.5                             30  4.9                                                                              24.1                                                                             35.5                                                                             2.1                                                                              13.4                                                                             6.0                                                                              0.8                                                                              4.4                                                                              13.0                                                                             0.9                                                                              5.0                                                                              15.0                                                                             2.7                                                                              2.3                                                                              0.9                             __________________________________________________________________________

It is observed a clear improvement of the catalytic properties(particularly activity and selectivity) of the mordenite exchanged withammonium ions and calcined in the presence of steam (M₁ ^(w) as comparedto that (M₁ ^(d)) calcined under dry air atmosphere.

It is observed that mordenite M₂ ^(w) gives substantially the sameresults as mordenite m₂ ^(d).

On the contrary, the nickel mordenites (M₄ ^(w)), cobalt mordenites (M₃^(w)) and silver mordenites (M₅ ^(w)), directly calcined in the presenceof steam, have a very poor selectivity as compared to the samemordenites calcined under dry air atmosphere, i.e. they result in asubstantial loss of aromatics: a strong hydrogenolysis, in particularwith a very substantial production of methane, is observed. In thelatter case, the low ethylbenzene content of C₈ aromatics is to beobserved; this result is probably due to the deethylation byhydrogenolysis of ethylbenzene.

EXAMPLE 6

Results of tests with catalysts M₁ ^(dw) to M₇ ^(dw), calcinated firstunder dry air and then, in the presence of steam.

The results are reported in the following tables 7, 8 and 9.

                                      TABLE 7                                     __________________________________________________________________________                                Ethylbenzene                                          Conversion                                                                          Loss of     C.sub.8                                                                             in C.sub.8                                        TIME                                                                              rate  Aromatics                                                                           Benzene                                                                             Aromatics                                                                           Aromatics                                         (h) M.sub.1.sup.dw                                                                   M.sub.2.sup.dw                                                                   M.sub.1.sup.dw                                                                   M.sub.2.sup.dw                                                                   M.sub.1.sup.dw                                                                   M.sub.2.sup.dw                                                                   M.sub.1.sup.dw                                                                   M.sub.2.sup.dw                                                                   M.sub.1.sup.dw                                                                    M.sub.2.sup.dw                                __________________________________________________________________________     1  32.1                                                                             34.2                                                                             1.3                                                                              2.9                                                                              13.2                                                                             13.4                                                                             15.1                                                                             15.3                                                                             1.3 1.6                                            3  28.7                                                                             29.8                                                                             1.4                                                                              1.7                                                                              11.7                                                                             12.0                                                                             13.3                                                                             13.7                                                                             1.3 1.4                                           10  24.2                                                                             18.2                                                                             1.1                                                                              2.3                                                                              9.8                                                                              6.8                                                                              11.2                                                                             7.8                                                                              1.2 1.4                                           30  16.1                                                                             7.3                                                                              0.7                                                                              1.8                                                                              6.5                                                                              2.3                                                                              7.5                                                                              2.6                                                                              0.9 1.2                                           __________________________________________________________________________

                                      TABLE 8                                     __________________________________________________________________________                                            Ethylbenzene                              Conversion                                                                             Loss of           C.sub.8  in C.sub.8                            TIME                                                                              rate     Aromatics                                                                              Benzene  Aromatics                                                                              Aromatics                             (h) M.sub.3.sup.dw                                                                   M.sub.4.sup.dw                                                                   M.sub.5.sup.dw                                                                   M.sub.3.sup.dw                                                                   M.sub.4.sup.dw                                                                   M.sub.5.sup.dw                                                                   M.sub.3.sup.dw                                                                   M.sub.4.sup.dw                                                                   M.sub.5.sup.dw                                                                   M.sub.3.sup.dw                                                                   M.sub.4.sup.dw                                                                   M.sub.5.sup.dw                                                                   M.sub.3.sup.dw                                                                   M.sub.4.sup.dw                                                                   M.sub.5.sup.dw                  __________________________________________________________________________     1  39.7                                                                             43.1                                                                             42.1                                                                             4.1                                                                              4.3                                                                              3.1                                                                              15.2                                                                             16.6                                                                             16.7                                                                             17.4                                                                             19.0                                                                             19.1                                                                             1.9                                                                              1.7                                                                              1.2                              3  36.8                                                                             41.9                                                                             41.0                                                                             33.9                                                                             4.1                                                                              2.9                                                                              14.0                                                                             16.2                                                                             16.3                                                                             15.1                                                                             1.8.5                                                                            18.7                                                                             1.8                                                                              1.6                                                                              1.2                             10  320                                                                              38.4                                                                             38.5                                                                             2.8                                                                              3.9                                                                              2.5                                                                              12.5                                                                             14.8                                                                             15.4                                                                             14.3                                                                             16.9                                                                             17.6                                                                             1.8                                                                              1.6                                                                              1.3                             30  26.0                                                                             31.0                                                                             31.9                                                                             2.9                                                                              3.2                                                                              2.8                                                                              9.9                                                                              11.9                                                                             12.5                                                                             13.5                                                                             14.2                                                                             11.4                                                                             1.4                                                                              1.4                                                                              1.1                             __________________________________________________________________________

                                      TABLE 9                                     __________________________________________________________________________                                Ethylbenzene                                          Conversion                                                                          Loss of     C.sub.8                                                                             in C.sub.8                                        TIME                                                                              rate  Aromatics                                                                           Benzene                                                                             Aromatics                                                                           Aromatics                                         (h) M.sub.6.sup.dw                                                                   M.sub.7.sup.dw                                                                   M.sub.6.sup.dw                                                                   M.sub.7.sup.dw                                                                   M.sub.6.sup.dw                                                                   M.sub.7.sup.dw                                                                   M.sub.6.sup.dw                                                                   M.sub.7.sup.dw                                                                   M.sub.6.sup.dw                                                                    M.sub.7.sup.dw                                __________________________________________________________________________     1  45.6                                                                             43.6                                                                             6.1                                                                              6.9                                                                              16.9                                                                             15.7                                                                             19.3                                                                             17.9                                                                             2.1 2.4                                            3  40.1                                                                             38.2                                                                             5.0                                                                              6.0                                                                              15.0                                                                             13.8                                                                             17.2                                                                             15.8                                                                             2.0 2.0                                           10  36.8                                                                             32.1                                                                             3.9                                                                              4.5                                                                              14.1                                                                             11.8                                                                             16.1                                                                             13.5                                                                             1.9 1.9                                           30  27.5                                                                             29.7                                                                             3.8                                                                              3.9                                                                              10.1                                                                             11.0                                                                             11.6                                                                             12.6                                                                             1.8 1.7                                           __________________________________________________________________________

The following observations are made:

Calcination under dry air and then in the presence of steam givesresults of the same order of magnitude as direct calcination in thepresence of wet air with the mordenite exchanged with ammonium ions(comparison of catalysts M₁ ^(w) and M₁ ^(dw)). For the mordenite of Hform (comparison of M₂ ^(wd) and M₂ ^(w)), the calcination under dryair, and then in the presence of steam, has the advantage, as comparedto a mordenite directly calcined in the presence of wet air, of giving abetter conversion rate at the beginning of the reaction, but thisconversion rate decreases considerably after 30 hours of the run.

On the contrary, the type of calcination according to the invention (dryair and then wet air) makes it possible to obtain a much more selectivecatalyst than that obtained by dry calcination or by direct calcinationin the presence of wet air with a mordenite exchanged with nickel,cobalt or silver. The catalysts M₃ ^(dw), M₄ ^(dw) and M₅ ^(dw) arerespectively more selective than M₃ ^(d), M₄ ^(d) and M₅ ^(d) or M₃^(w), M₄ ^(w) and M₅ ^(w).

EXAMPLE 7

Results of tests with catalysts M₁ ^(wd), M₂ ^(wd), M₃ ^(wd), M₄ ^(wd),M₅ ^(wd), first calcinated under wet air and then under dry air.

It has been observed that exactly the same results are obtained thanwith samples M₁ ^(w), M₂ ^(w), M₃ ^(w), M₄ ^(w) and M₅ ^(w), whichresults are reported in tables 5 and 6 above.

EXAMPLE 8

A nickel mordenite M₈, doped with copper, is prepared as follows: 100 gof uncalcined solid M₁, whose preparation has been described in example1, are subjected to an ion exchange identical to that used for thepreparation of solid N₄, in a solution of nickel nitrate. The resultingsolid is dried at 200° C. for 4 hours, cooled and subjected to a dryimpregnation (without excess of solution) with an adequate volume of anaqueous solution containing 0.1 g of copper in the form of coppernitrate. The resulting product is dried at 85° C. for 6 hours in an airdrying oven and then, separated in three equal portions which arerespectively calcined according to the three forms of procedure No. 1, 2and 3, as defined in example 3.

There are thus obtained solids M₈ ^(d), M₈ ^(w) and M₈ ^(dw).

EXAMPLE 9

A palladium mordenite M₉ is prepared as follows: 100 g of uncalcinedsolid M₁, prepared as in example 1, are immersed in 525 cc of a solutioncontaining 0.0525 mole of palladium nitrate and 10 cc of a 40% HClsolution. The exchange takes place at room temperature for 6 hours understirring. The product is then washed twice, successively with 1 liter ofdistilled water, dried at 85° C. for 6 hours and then separated in threeequal portions which are respectively calcined as hereabove stated inexample 3, according to forms of procedure No. 1, 2 and 3. There arethus obtained solids M₉ ^(d), M₉ ^(w) and M₉ ^(dw).

Table 10 below gives analyzes of both solids M₈ and M₉.

                  TABLE 10                                                        ______________________________________                                                            % by                                                                SiO.sub.2 /Al.sub.2 O.sub.3                                                             weight  Additional                                                                            % by weight                               CATALYSTS Molar     Na      mertal  metal                                     ______________________________________                                        M.sub.8   10.9      <0.3        Ni        1.5                                                                 Cu        0.1                                 M.sub.9   ˜10.9                                                                             <0.3        Pd        0.1                                 ______________________________________                                    

The 6 catalysts obtained are subjected to a test of toluene dismutationunder the same conditions as those indicated at the end of example 3.

EXAMPLE 10

Results of the test of catalysts M₈ ^(d), M₈ ^(w) and M₈ ^(dw). Theseresults are reported in table 11 below.

                                      TABLE 11                                    __________________________________________________________________________        Conversion                                                                             Loss of                                                          TIME                                                                              rate     aromatics                                                                              Benzene  C.sub.8 aromatics                                                                      Ethylbenzene                          (h) M.sub.8.sup.d                                                                    M.sub.8.sup.w                                                                    M.sub.8.sup.dw                                                                   M.sub.8.sup.d                                                                    M.sub.82                                                                         M.sub.8.sup.d                                                                    M.sub.8.sup.d                                                                    M.sub.8.sup.w                                                                    M.sub.8.sup.w                                                                    M.sub.8.sup.w                                                                    M.sub.8.sup.w                                                                    M.sub.8.sup.dw                                                                   M.sub.8.sup.w                                                                    M.sub.8.sup.dw                     __________________________________________________________________________     1  31.0                                                                             41.6                                                                             42.5                                                                             9.6                                                                              6.4                                                                              4.9                                                                              9.5                                                                              15.6                                                                             16.6                                                                             11.0                                                                             17.9                                                                             19.1                                                                             1.7                                                                              1.6                                                                              1.5                              3  28.9                                                                             39.7                                                                             40.3                                                                             6.5                                                                              4.9                                                                              4.0                                                                              10.0                                                                             15.5                                                                             16.2                                                                             11.5                                                                             17.8                                                                             18.6                                                                             1.8                                                                              1.7                                                                              1.3                             10  22.6                                                                             36.1                                                                             37.9                                                                             6.1                                                                              4.6                                                                              4.0                                                                              7.3                                                                              13.9                                                                             15.0                                                                             8.5                                                                              16.0                                                                             17.2                                                                             19 1.5                                                                              1.2                             30  18.7                                                                             32.0                                                                             32.6                                                                             5.0                                                                              4.9                                                                              3.3                                                                              11.9                                                                             12.7                                                                             6.9                                                                              13.7                                                                             14.6                                                                             1.9                                                                              1.9                                                                              1.0                                __________________________________________________________________________

It will be observed that catalyst M₈ ^(dw), calcined in dry medium andthen in wet atmosphere, has an activity and a selectivity substantiallyof the same order of magnitude as catalyst M₄ ^(dw), calcined under thesame conditions.

EXAMPLE 11

Results of the tests of catalysts M₉ ^(d), M₉ ^(w) and M₉ ^(dw). Theresults are reported in table 12 below.

                                      TABLE 11                                    __________________________________________________________________________        Conversion                                                                             Loss of                                                          TIME                                                                              rate     aromatics                                                                              Benzene  C.sub.8 aromatics                                                                      Ethylbenzene                          (h) M.sub.8.sup.d                                                                    M.sub.8.sup.w                                                                    M.sub.8.sup.dw                                                                   M.sub.9.sup.d                                                                    M.sub.9w                                                                         M.sub.9.sup.dw                                                                   M.sub.9.sup.d                                                                    M.sub.9.sup.w                                                                    M.sub.9.sup.dw                                                                   M.sub.9.sup.d                                                                    M.sub.9.sup.w                                                                    M.sub.9.sup.dw                                                                   M.sub.9.sup.d                                                                    M.sub.9.sup.w                                                                    M.sub.9.sup.dw                  __________________________________________________________________________     1  34.2                                                                             39.3                                                                             41.7                                                                             7.9                                                                              6.7                                                                              4.0                                                                              11.5                                                                             14.3                                                                             13.3                                                                             16.5                                                                             16.5                                                                             19.1                                                                             1.8                                                                              1.9                                                                              1.5                              3  31.2                                                                             37l.1                                                                            11.5                                                                             5.3                                                                              4.8                                                                              3.5                                                                              11.4                                                                             14.2                                                                             16.7                                                                             13.1                                                                             16.3                                                                             19.1                                                                             1.7                                                                              1.8                                                                              1.3                             10  30.5                                                                             35.0                                                                             38.1                                                                             4.6                                                                              4.2                                                                              3.2                                                                              11.3                                                                             13.2                                                                             15.3                                                                             13.0                                                                             15.2                                                                             17.6                                                                             .5 1.7                                                                              153                             30  26.1                                                                             32.6                                                                             33.6                                                                             4.1                                                                              3.0                                                                              9.6                                                                              12.2                                                                             13.4                                                                             11.0                                                                             14.1                                                                             15.4                                                                             1.5                                                                              1.7                                                                              1.1                                __________________________________________________________________________

It is observed that calcination under wet air (M₉ ^(w)) and particularlythat which is preceded with a calcination under dry air atmosphere (M₉^(dw)) provides for a clear improvement of the activity and selectivityas compared with the catalyst calcined only dry air.

What I claim is:
 1. In a process for dismutation and transalkylation ofalkyl aromatic hydrocarbons in the presence of a catalyst, theimprovement comprises employing as said catalyst a mordenite containingless than 0.5% by weight of sodium, wherein the molar ration SiO₂ /Al₂O₃ is in the range from 10 to 100, the mordenite further containing atleast one metal selected from cobalt, nickel, silver and palladium, saidcatalyst having been produced by a process comprising eliminating themajor portion of sodium from a mordenite in the sodium form; saidmordenite having a molar ratio SiO₂ /Al₂ O₃ of about 10, said catalystbeing obtained by incorporating said metal to said mordenite and dryingof the resulting catalyst mass at about 50° to 150° C., and subjectingthe resultant dried catalyst to a dry calcination between 300 and 700°C., in the presence of an inert or oxidizing dry gas containing lessthan 1% by volume of steam and then subjecting resultant calcinedcatalyst to a wet calcination between 250° and 700° C., in the presenceof at least one gas selected from steam, an inert gas and an oxidizinggas, the inert or oxidizing gas containing by volume at least 3% ofsteam.
 2. A process according to claim 1, wherein the metal, selectedfrom cobalt, nickel, silver and palladium, is introduced in the catalystby direct exchange of the sodium ions of the initial mordenite used forthe manufacture of the catalyst, with metal ions selected from cobalt,nickel, silver and palladium.
 3. A process according to claim 1, whereinthe metal selected from cobalt, nickel, silver and palladium isintroduced in the catalyst by first proceeding to an exchange of thesodium ions of the initial mordenite used for the manufacture of thecatalyst, with H⁺ or NH₄ ⁺ ions, this exchange being followed eitherwith an exchange of H⁺ or NH₄ ⁺ ions with the ions of at least one metalselected from cobalt, nickel, silver and palladium or with animpregnation of the the mordenite with at least one metal selected fromcobalt, nickel, silver and palladium.
 4. A process according to claim 1,wherein said dry gas contains less than 0.25% of steam by volume.
 5. Aprocess according to claim 1, wherein the wet calcination is performedwith steam.
 6. A process according to claim 1, wherein the wetcalcination is performed by means of a mixture of steam with an inert oroxidizing gas, said mixture containing at least 10% by volume of steam.7. A process according to claim 1, wherein the wet calcination isperformed directly after the so-called "dry" first calcination, withoutany cooling step between the two dry and wet calcination steps.
 8. Aprocess according to claim 1, wherein the dry calcination in thepresence of a dry gas is followed with the cooling of the resultingcatalyst mass before proceeding to the wet second calcination.
 9. Aprocess according to claim 1, wherein the wet calcination is conductedbetween 350° and 600° C., under a pressure from 0.5 to 10 bars.
 10. Aprocess according to claim 1, wherein said at least one metal is nickeland wherein copper is also added as an additional metal.
 11. A processaccording to claim 1 wherein the wet calcination is conducted at300°-650° C.